Everyone in Washington claims to want the same thing lately: a “serious conversation” about health-care costs. So let’s have one.

Republicans have a plan that has been tried repeatedly but that has never worked. Democrats have a plan that might work in theory, but it is untested at the scale they’ll need for it to work in practice. And both parties are too scared to talk about the only plan that has worked.

But before we get to that plan, I want to tell you about a graph.

I found it buried inside a Kaiser Family Foundation brief entitled “Health Care Spending in the United States and Selected OECD Countries.” Inauspicious, maybe. But it should change the way we think about health-care costs. Because what it shows is that we’ve failed. Failed to control costs. Failed to restrain the growth of government.

And it shows something else, too: Where we’ve failed, others have succeeded.

Everyone knows — or should know — that the United States spends much more than any other country on health care. But the Kaiser Family Foundation broke that spending down into two parts: the government’s share and the private sector’s share (both measured as a percentage of total gross domestic product), then compared the results to figures from 12 other countries that are members of the Organisation for Economic Co-operation and Development. And here’s the shocker: Our government spends more on health care than the governments of Japan, Australia, Norway, the United Kingdom, Spain, Italy, Canada or Switzerland.

Think about that for a minute. Canada has a single-payer health-care system. The government is the only insurer of any note. The United Kingdom has a socialized system, in which the government is not only the sole insurer of note but also employs most of the doctors and nurses and runs most of the hospitals. And yet, measured as a share of the economy, our government health-care system is the largest of the bunch.

And it’s worse than that: Atop our giant government health-care sector, we have an even more giant private health-care sector. Altogether, we’re spending about 16 percent of the GDP on health care. No other country even tops 12 percent. Which means we’ve got the worst of both worlds: huge government and high costs.

This is where a “serious conversation” on health-care costs would start — with what has worked, and what we can learn from it. Instead, it’s where our conversation about health-care costs never quite goes.

The Republican plan, in fact, heads in the opposite direction: The GOP outsources Medicare to private insurers and gives senior citizens checks that cover less and less of the cost of insurance every year. Republicans hope that when faced with more cost pressure and more options, seniors will be able to exert the sort of consumer pressure that lowers prices while retaining, or even improving, quality.

What they’ve got in mind already exists in Medicare. “Our premium-support plan is modeled after the Medicare Part D prescription-drug program,” Paul Ryan (R-Wis.) told me. But Part D hasn’t controlled costs. Instead, premiums have risen by 57 percent since 2006, and the program is expected to see nearly 10 percent growth in annual costs over the next decade.

Moreover, this isn’t the first time we’ve tried to let private insurers into Medicare to work their magic. The Medicare Advantage program, which invited private insurers to offer managed-care options to Medicare beneficiaries, was expected to save money, but it ended up costing about 120 percent of what Medicare costs.

The Democratic plan, conversely, quietly recognizes that government-run health-care systems that are willing to throw their weight around can control costs. So the plan is to have Medicare try to pay for quality, not volume.

The first step is figuring out what quality is. So Medicare has been collecting vast amounts of hospital data on patients’ experiences, the delivery of pre-operative antibiotics, the prevalence of medical imaging and other topics. Come October, the hospitals posting good numbers will get a bonus from the Affordable Care Act; those posting bad numbers will face a penalty. Next year, the bonus and penalty will get bigger. Democrats have also created and funded a center to start testing the effectiveness of various drug, device and surgical treatments.

As for the inevitable political blowback, Democrats created the Independent Payment Advisory Board, a panel of 15 Senate-confirmed health-care experts who can make tough, cost-cutting reforms to Medicare in Congress’s stead. To be stopped, Congress needs to vote the board down, and the president needs to sign off on lawmakers’ opposition. That creates ample room for Congress to hand the IPAB the decisions it doesn’t want to make on its own.

Could it work? Sure. But it’s a gamble. It’s easy to imagine that strategy improving quality without cutting costs. That’d leave us with a better health-care system than we have now but the same budget problems. Another danger is that Congress could override the IPAB, rendering it useless as a tool for cost control.

But that’s the choice we’ve been left with: a plan that has never worked or a plan that’s never been tried. As for the approach that’s helped every other industrialized country achieve universal coverage at about half our costs? Well, we’re still not ready to talk about that.